As for the US 27/68 signage, that unknown shield says "Formerly Exit 17." For years, the only exit numbers posted on I-75 in Kentucky were sequentially-numbered exits for KY 418 (Exit 15), US 60 (Exit 16), US 27/68 (Exit 17), and KY 922 (Exit 18). There was no exit number for I-64 east since it wasn't considered a Lexington exit. When Kentucky adopted mileage-based exit numbers and posted them at all interchanges, the Lexington exits briefly had "Formerly..." signs to denote the old exit numbers.
That is very interesting. That's the first time I've heard of former exit numbers being posted in a shield like that.
I remember the old exit numbers being posted, but had forgotten exactly how they were posted. Since Kentucky uses demountable route markers and copy on guide signs, it was easy to put that indicator up on the sign and move the US 27 and US 68 markers to accommodate it.
With those exit numbers - the unposted numbers going south would have probably corresponded to all of the exits that were originally built?
Yes, but I think one of the exits was a later addition.
Going from south to north from Exit 15 (KY 418), the old exits I remember are:
US 25/421 north Clays Ferry
US 25/421 south Clays Ferry
US 227 Boonesborough/Winchester (now KY 627)
US 25/421 Richmond
KY 876 Richmond
KY 21 Berea
US 25 Mt. Vernon/Renfro Valley
US 25 Mt. Vernon/Livingston
KY 909 Livingston
KY 80 London
KY 192 London
US 25E Corbin
US 25W Corbin
US 25W Williamsburg
KY 92 Williamsburg
Only problem is, that's 15 exits right there. So one of the exits was added later after the Lexington sequential exits were established (and remember that I-64 didn't have an exit number).
My guess for the added exit that threw the sequence out of whack is the KY 909 Livingston exit. That road leading down to US 25 is of more modern construction than most in the area.